The artwork shows the 100 heaviest meteorites found and seen falling to earth. For each meteorite it is represented on the arched timeline: the year in which it was found or it has fallen, the weight (indicated by the size of the circle) and its category.
Source: Nasa
https://www.behance.net/gallery/31058715/THE-BIGGEST-METEORITES-FALLEN-ON-HEARTH-Corriere